Bonding a thermoplastic elastomer to a magnesium based metal

ABSTRACT

In one embodiment, the present invention relates to a bonded assembly made of a magnesium containing metal comprising at least about 25% by weight magnesium, a thermoplastic elastomer, and an adhesive between the magnesium containing metal and the thermoplastic elastomer, the adhesive comprising from about 20% to about 99% by weight of a polymeric material.

This is a division of application Ser. No. 09/336,882, filed Aug. 18,1999 now U.S. Pat. No. 6,287,411.

FIELD OF THE INVENTION

The invention relates to bonding a thermoplastic elastomer to amagnesium based metal. More specifically, the invention relates to athermoplastic elastomer strongly bonded to a magnesium containing metalusing a specifically defined adhesive.

BACKGROUND OF THE INVENTION

Bonding organic materials such as rubbers and plastics to metals is ofgreat importance. Numerous articles provide a litany of mechanisms andsolutions for bonding these distinct materials, with varying degrees ofsuccess. This is because different organic materials and metals haveunique properties and varying degrees of compatibility.

For example, some organic materials have low energy surfaces while otherorganic materials have high energy surfaces. Some organic materials haveplastic properties while other organic materials have elastomericproperties. Some organic materials have good heat resistance while otherorganic materials have poor heat resistance. Some organic materials havea high melt index while other organic materials have a low melt index.Organic materials may have different atoms which affect bondingproperties, such as nitrogen containing materials, oxygen containingmaterials, silicon containing materials, halogen containing materials,sulfur containing materials, and so on.

Metals and metal alloys (collectively termed metals) possess varyingcharacteristics. Metals vary in hardness/softness, corrosion resistance,toughness, wear resistance, resistance to chemical attack, tensilestrength, types of oxides formed, and so on. With specific regard tomagnesium, it is much more reactive than many other metals. Magnesiumhas a high sensitivity to salts such as chlorides. Magnesium also easilyand quickly oxidizes. Magnesium oxide, formed by oxidation on amagnesium surface, is a very difficult surface on which to form a strongbond with other materials. Extreme care must be exercised with magnesiumas fire and explosion hazards are associated with magnesium dust.

There are seemingly endless permutations of organic materials, andmetals, all of which inherently have varying characteristics andproperties. Improved bonding between specific types of organic materialsand metals is therefore desired.

Furthermore, bonding organic materials to metals typically involvesinitially contacting the metal surface with a primer prior to joiningthe organic material with the metal. The primer serves improve adhesionbetween an adhesive and the metal. The primer, which strongly bonds withthe adhesive, more strongly bonds to the metal than the adhesive.However, the use of a primer is not only time consuming, but alsoexpensive. The use of additional chemicals such as primers andassociated solvents presents disposal concerns and toxicity concerns.Bonding organic materials to metals without the need of a primer istherefore also desired.

Products made of an organic material bonded to a metal are used in manyenvironments. Many of these products are used in harsh manufacturingenvironments. Manufacturing environments involve drastic and suddenchanges in temperature and humidity, shock resistance (for example, toabsorb the shock of a drop on concrete from a height of four feet), theability to absorb vibrational movement, and resistance to petroleumbased products, water-based cutting fluids, and industrial chemicals andsolvents. There is a desire for products having organic materials tometals that maintain their integrity over time even in a manufacturingenvironment.

SUMMARY OF THE INVENTION

In one embodiment, the present invention relates to a bonded assemblymade of a magnesium containing metal comprising at least about 25% byweight magnesium, a thermoplastic elastomer, and an adhesive between themagnesium containing metal and the thermoplastic elastomer, the adhesivecomprising from about 20% to about 99% by weight of a polymericmaterial.

In another embodiment, the present invention relates to a bondedassembly made of a magnesium containing metal comprising from about 50%to about 99% by weight of magnesium and from about 1% to about 50% byweight of a non-magnesium metal, an olefinic thermoplastic elastomer,and an adhesive between the magnesium containing metal and thethermoplastic elastomer, the adhesive comprising from about 20% to about99% by weight of at least one polymeric material and from about 1% toabout 80% by weight of at least one polymeric complimentary material.

In yet another embodiment, the present invention relates to an apparatusmade of a magnesium containing metal comprising from about 50% to about99% by weight of magnesium and from about 1% to about 50% by weight of anon-magnesium metal, a chlorinated olefinic thermoplastic elastomer, anda heat activated solvent based adhesive between the magnesium containingmetal and the thermoplastic elastomer, the adhesive comprising fromabout 20% to about 99% by weight of a halogenated polyolefin and fromabout 1% to about 80% by weight of at least one polymeric complimentarymaterial.

In still yet another embodiment, the present invention relates to amethod of making a bonded assembly involving applying an adhesive to atleast a portion of a magnesium containing metal to provide an adhesivecoated metal, the adhesive comprising from about 20% to about 99% byweight of a polymeric material and the magnesium containing metalcomprising at least about 25% by weight magnesium, and contacting theadhesive coated metal with a thermoplastic elastomer under sufficientpressure for a sufficient period of time to bond the thermoplasticelastomer to the adhesive coated metal.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to effectively bonding thermoplasticelastomers to a magnesium containing metal. The thermoplastic elastomersmaintain strong adhesion to magnesium containing metals over time evenin harsh environments, where drastic and sudden changes in temperatureand humidity, shock resistance, the ability to absorb vibrationalmovement, and resistance to petroleum based products, water-basedcutting fluids, and industrial chemicals and solvents are encountered.While not being bound by any specific mechanism or theory, it isspeculated that the adhesive containing a polymeric material stronglybonds to both thermoplastic elastomers and magnesium containing metals.

Magnesium containing metals include pure magnesium, substantially puremagnesium, and magnesium alloys. Magnesium alloys contain at least about25% by weight magnesium. In one embodiment, magnesium alloys contain atleast about 50% by weight magnesium. In another embodiment, magnesiumalloys contain at least about 75% by weight magnesium. In yet anotherembodiment, magnesium alloys contain at least about 85% by weightmagnesium.

Magnesium alloys contain magnesium and one or more of an alkali metal,an alkaline earth metal, a transition metal, a rare earth metal, othermetals and certain non-metals. General examples of magnesium alloys arealloys containing magnesium and one or more of aluminum, chromium,cobalt, copper, iridium, iron, gold, manganese, nickel, rare earthmetals such as lanthanum, cerium, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium, ytterbium and lutetium, palladium, platinum, scandium, silicon,silver, tin, titanium, yttrium, zinc and zirconium.

Specific examples of magnesium alloys include the following ASTMdesignations: AM100A; AZ63A; AZ81A; AZ91C,E; AZ92A; EZ23A; QE22A; WE43A;WE54A; ZE41A; ZE63A; ZK51A; ZK61A; AM50A; AE42X1; AM60A,B; AS41A,B;AZ91B,D; AZ31B,C; AZ61A; AZ80A; and ZK60A.

In one embodiment, the magnesium containing metal contains from about25% to about 100% by weight of magnesium and from 0% to about 75% byweight of one or more non-magnesium compounds, such as one or more of analkali metal, an alkaline earth metal (but not magnesium), a transitionmetal, a rare earth metal, other metals and certain non-metals. Inanother embodiment, the magnesium containing metal contains from about50% to about 99% by weight of magnesium and from about 1% to about 50%by weight of one or more non-magnesium compounds or metals, such as fromabout 1% to about 50% by weight of aluminum. In yet another embodiment,the magnesium containing metal contains from about 75% to about 98% byweight of magnesium and from about 25 2% to about 25% by weight of oneor more non-magnesium compound, such as from about 2% to about 25% byweight of aluminum, zinc and manganese.

In one embodiment, a primer is not applied to the magnesium containingmetal prior to bonding with the thermoplastic elastomer using anadhesive as defined below. In another embodiment, a paint is not appliedto the magnesium containing metal in order to increase bond strengthprior to bonding with the thermoplastic elastomer using an adhesive. Thepresent invention provides a bonded assembly wherein minimal processingof the magnesium containing metal prior to bonding is possible.

In many embodiments, it is preferable to clean at least the bondingsurface of the magnesium containing metal prior to bonding with thethermoplastic elastomer.

Cleaning may be conducted by at least one of a water rinse a deionizedwater rinse, a dilute acid wash, and a mild acid wash. Any mineral ororganic acid may be employed to wash the metal surface, so long as thesurface of the magnesium containing metal is not substantially degradedor damaged.

In one embodiment, the magnesium containing metal is contacted with achromate solution prior to bonding with the thermoplastic elastomerusing an adhesive as defined below. A chromate solution contains waterand chromate ions.

The chromate solution does not deposit any substantial amount of acoating on the magnesium containing metal, but it does alter the surfacevia oxidation. Contact is accomplished by spraying or dipping themagnesium containing metal in a chromate solution. Chromate may bederived from a number of sources including chromic acid, sodiumdichromate, potassium chromate and magnesium chromate. In oneembodiment, the concentration of chromate in the chromate solution isfrom about 0.1 g/l to about 25 g/l. In another embodiment, theconcentration of chromate in the chromate solution is from about 1 g/lto about 5 g/l. In one embodiment, the magnesium containing metal is incontact with the chromate solution from about 2 seconds to about 2minutes, preferably from about 5 seconds to about 1 minute, and morepreferably from about 10 seconds to about 30 seconds.

The chromate solution may further contain additives including at leastone of hybrofluozirconic acid and fluoroboric acid. In some embodiments,contacting the magnesium containing metal with the chromate solutionfacilitates strong adhesion between the adhesive and the magnesiumcontaining metal.

Thermoplastic elastomers are occasionally referred to as syntheticrubbers, but are more accurately referred to as elastoplastics.Thermoplastic elastomers are polymeric materials having both plastic andelastomeric properties. In one embodiment, the thermoplastic elastomersinclude olefinic thermoplastic elastomers and chlorinated thermoplasticelastomers. In a preferred embodiment, the thermoplastic elastomersinclude chlorinated olefinic thermplastic elastomers. General examplesof olefinic thermoplastic elastomers, chlorinated thermoplasticelastomers, and chlorinated olefinic thermoplastic elastomers includepolyolefines, polyvinylchloride-nitrile rubber blends such aspolyvinylchloride-acrylonitrile-butadiene elastomer blends,polyvinylchloride-copolyester elastomer blends,polyvinylchloride-polyurethane elastomer blends, polychloroprenes, andchlorinated polyethylenes. Random, block, and graft copolymers of any ofone or more thereabove also constitute thermoplastic elastomers inaccordance with the present invention.

Polyolefins include polymer and copolymers of monoolefins having from 2to about 20 carbon atoms and more preferably from 2 to about 12 carbonatoms per molecule. Monoolefins useful for making polyolefins preferablycontain a terminal olefin bond and these include ethylene, propylene,1-butene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-butene, 1-octene,1-decene and 4-ethyl-1-hexene. Examples of such homopolymers includepolyethylene (including low density, medium density, high density,linear low density and ultralow density polyethylene), polypropylene(including low density, high density and isotactic polypropylene),poly-1-butene, poly-3-methyl-1-butene and poly-4-methyl-1-pentene.Copolymers including ethylene and higher olefins such as propylene arepreferred. Polyolefin copolymers include a polyolefin and anotherpolymeric material such as polystyrene, isoprene, and butadiene.

In one embodiment, the thermoplastic elastomers used in accordance withthe present invention are melt processable rubbers. The thermoplasticelastomers can thus be made using general-purpose thermoplasticequipment including injection molding machines, extruders, calendars,and the like. In one embodiment, the thermoplastic elastomers used inaccordance with the present invention are single phase polymer systems.In another embodiment, the thermoplastic elastomers used in accordancewith the present invention are substantially amorphous polymer systems.

In one embodiment, the thermoplastic elastomer comprises a meltprocessible, thermoplastic elastomeric blend of an ethylene copolymerand a vinyl or vinylidene halide polymer. In one specific embodiment, ispartially crosslinked, thermoplastic, melt-processible, elastomericblend of (a) a copolymer of ethylene, one or more ethylenicallyunsaturated organic monomers preferably other than an unsaturatedcarboxylic acid, and optionally at least one additional monomer of anethylenically unsaturated C₃-C₂₀ carboxylic acid, carbon monoxide, andsulfur dioxide; and (b) between about 5% and about 75% by weight, basedon the entire blend, of a vinyl or vinylidene halide polymer wherein thecomonomer content in (a) is such that the ethylene copolymer iscompatible with the vinyl or vinylidene halide polymer.

In another specific embodiment, is partially crosslinked, thermoplastic,melt-processible, elastomeric blend of (a) a copolymer of ethylene andone or more ethylenically unsaturated organic monomers of esters ofunsaturated C₃-C₂₀ mono- or dicarboxylic acids, vinyl esters ofsaturated C₂-C₁₈carboxylic acids, vinyl alkyl ethers wherein the alkylgroup has about 1 to about 18 carbon atoms, vinyl or vinylidene halides,acrylonitrile, methacrylonitrile, norbornene, alpha-olefins of about 3to about 12 carbon atoms, and vinyl aromatic compounds and (b) betweenabout 5% and about 75% by weight, based on the blend, of a vinyl orvinylidene halide polymer wherein the comonomer content in (a) is suchthat the-ethylene copolymer is compatible with the vinyl or vinylidenehalide polymer; the blend preferably (but not necessarily) notcontaining a polymerizable polyunsaturated compound or polymer of suchcompound.

The ethylene copolymers useful in this embodiment can be represented ashaving the formula E/X/Y, where E is an ethylene polymer, X is anethylenically unsaturated organic monomer preferably other than anunsaturated carboxylic acid, and Y is an ethylenically unsaturatedcarboxylic acid, carbon monoxide, or sulfur dioxide. Examples of theorganic monomers include one or more of esters of said unsaturated mono-or dicarboxylic acids, vinyl esters of saturated carboxylic acids wherethe acid group has from about 2 to about 18 carbon atoms, vinyl alkylethers wherein the alkyl group has from 1 to about 18 carbon atoms,vinyl or vinylidene halides, acrylonitrile, methacrylonitrile,norbornene, alpha-olefins having from about 3 to about 12 carbon atoms,and vinyl aromatic compounds. Preferred organic monomers include methylacrylate, butyl acrylate and vinyl acetate.

For the purpose of this invention, the term “polymerizable,polyunsaturated compound” means a non-polymeric compound having two ormore polymerizable double bonds, such as, e.g., triallyl cyanurate.Preferred organic monomers which can be copolymerized with ethyleneinclude methyl acrylate, butyl acrylate and vinyl acetate. Of course,more than one organic monomer may be copolymerized with ethylene to formthe ethylene copolymer useful in the practice of the subject invention.In these embodiments, the melt index range for these copolymers is 0.1to 1000 (ASTM D-1238), and preferably 1 to 100.

The ethylene copolymers preferably have sufficient comonomercopolymerized therein to exhibit compatability with the vinyl andvinylidene halide polymers described below. Generally speaking,copolymers having a comonomer content of greater than 45% based on theweight of the copolymer are particularly useful. A more detaileddiscussion of the compatability of these ethylene copolymers with vinyland vinylidene halide polymers, as well as a discussion of thepreparation of the copolymers can be found in Polymer-PolymerMiscibility, O.

Olabisi, L. M. Robeson and M. T. Shaw, Academic Press, N.Y., N.Y., 1979,U.S. Pat. No. 3,684,778 and U.S. Pat. No. 3,780,140, all of which areincorporated by reference herein.

The ethylene copolymers in these specific embodiments are blended withabout 5% to about 75%, preferably with about 20% to about 60%, by weightbased on the blended composition of vinyl or vinylidene halide polymersincluding copolymers resulting from copolymerization with a comonomer ofvinyl esters, acrylonitrile, acrylic esters, vinylidene chloride, vinylchloride, esters of unsaturated carboxylic acids and vinyl ethers. Forexample, polyvinyl chloride having an inherent viscosity of 0.30 to 1.4(ASTM D-1243) is generally useful.

The blending of the ethylene copolymer with the vinyl or vinylidenehalide polymer is accomplished by any one of a number of suitabletechniques, for example, in a Banbury mixer, two-roll mill or extruder.Blending is conducted at a temperature suitably high enough to softenthe polymers for adequate blending, but not so high as to degrade thevinyl or vinylidene halide polymer. Generally speaking, blendingtemperatures range from about 140° C. to about 200° C., and blending iscarried out for a time sufficient to homogeneously blend the components.

One aspect of these specific embodiments is the partial crosslinking ofthe ethylene copolymer in the compatible blend. This can be carried outusing any one or more of the well known crosslinking techniquesincluding electron beam irradiation, gamma irradiation and free radicalcuratives such as peroxides and/or azo compounds. The crosslinking ofthe ethylene copolymer can be carried out before or concurrently withblending with the vinyl or vinylidene halide polymers, or after suchblending when using radiation techniques to effectuate the crosslinking.

If the ethylene copolymer in the blend contains carbon monoxide,diamines such as methylene dianiline or p-phenylene diamine can be usedto effectuate the desired crosslinking. If the ethylene copolymer isethylene/vinyl acetate/carbon monoxide, sulfur vulcanizing agents can beused as detailed in U.S. Pat. No. 4,172,939, which is incorporated byreference for its relevant teachings. For crosslinking ethylenecopolymers containing carboxylic acid functionalities, the formation ofionic crosslinks is suitable, and is achieved with various metal oxidesor hydroxides such as ZnO and NaOH, or with organometallics such aschromium acetylacetone, as detailed in U.S. Pat. No. 4,304,887, which isincorporated by reference for its relevant teachings.

When crosslinking is effected in the presence of a free radicalgenerator, it is preferable, although not required, to add apolyunsaturated compound to the blend, such as m-phenylene-bis-maleimideor triallyl cyanurate, to improve the crosslinking efficiency and toreduce the amount of free radical generator required. When othercrosslinking methods are employed, such as curing with diamines, sulfur,or metal compounds, such polyunsaturated compounds are not used.

The term “partially crosslinked” refers to a degree of crosslinkingsufficient to transform a blend of an ethylene copolymer and a vinyl orvinylidene halide polymer into a thermoplastic elastomeric blend. Toquantify the degree of crosslinking, the amount of insoluble, and hencecrosslinked, polymer is determined by soaking a sample of the polymer,after crosslinking, in tetrahydrofuran at about 23° C. for about 16hours, isolating the insoluble portion and weighing the dried residue,making suitable corrections based upon knowledge of the composition. Forexample, the weight of components soluble in tetrahydrofuran such asplasticizers are subtracted from the initial weight; and componentsinsoluble in tetrahydrofuran, such as pigments, fillers, etc. aresubtracted from both the initial and final weight. The insoluble polymerrecovered is reported as percent gel content. This procedure is based ona conventional procedure for quantifying degree of crosslinking that ismore fully detailed in U.S. Pat. No. 3,203,937, which is herebyincorporated by reference in this regard. The polymer blends arepreferably partially crosslinked so that they have a gel content fromabout 5% to about 90%, preferably from about 10% to about 70% based onthe total polymer. The conditions under which this crosslinking iscarried out, i.e., type and quantity of crosslinking agent, crosslinkingtime and temperature, to arrive at a composition having a gel contentwithin this preferable range, can be determined empirically by oneskilled in the art. When chemical crosslinking agents are utilized, itis preferable that they be substantially totally consumed during thecrosslinking step.

When polyvinyl chloride (PVC) is utilized as the vinyl halide polymer,spectroscopic evidence indicates that the gel fractions isolated fromthose partially crosslinked polymer blends contain only crosslinkedethylene copolymer, with no or little detectable PVC present. Althoughnot wishing to be bound by any theory, it is believed that essentiallyno crosslinking of the PVC occurs.

In a preferred embodiment, the thermoplastic elastomers are meltprocessible using conventional plastic processing equipment. Articlesmolded from the unique thermoplastic elastomers of the present inventionexhibit properties generally only associated with vulcanized rubber. Forexample, the thermoplastic elastomers have resistance to compression setvalues of about 20% to about 70% (about 70° C. to about 100° C.); andelongation at break values of about 150% to about 600% withoutsubstantial permanent tensile set (i.e., less than about 15%).

In a most preferred embodiment, the thermoplastic elastomer comprises apartially crosslinked chlorinated olefin interpolymer alloy (withcompounds described below). In this connection, thermoplastic elastomerin one embodiment comprises an alloy of a polyolefin such as ethyleneand a chlorinated polyolefin wherein the olefin polymer component ispartially crosslinked in situ. Such thermoplastic elastomers arecommercially available under the trade designation Alcryn® fromDuPont/Advanced Polymer Alloys under the designators Series 1000, Series2000, Series 3000, and Series 4000.

Various additives, alloying compounds, blending compounds and/orcompounding materials are optionally incorporated into the thermoplasticelastomer composition. Additives include plasticizers, UV stabilizers,antioxidants, adhesion promoters, rheology modifiers, antiozoants, dyes,calcium carbonate, carbon black, clays, colorants, tackifiers,lubricants, waxes, and non-reinforcing fillers.

The thermoplastic elastomers optionally contain alloying compounds,blending compounds and compounding materials such as natural andsynthetic rubbers, thermoplastics, thermosets, other thermoplasticelastomers such as styrenic thermoplastic elastomers, polyesterthermoplastic elastomers, polyamide thermoplastic elastomers, andpolyurethane thermoplastic elastomers. In one embodiment, natural andsynthetic rubbers are optionally incorporated into the thermoplasticelastomer. Natural and synthetic rubbers, such as nitrile rubber,contribute to the oil resistance of thermoplastic elastomers. In apreferred embodiment, the thermoplastic elastomers are a blend of two ormore polymeric materials.

Additional examples of commercially available thermoplastic elastomersinclude those under the trade designation Telcar® from B.F. Goodrich;those under the trade designation TPR® from Uniroyal; those under thetrade designation Somel® and Hytrel® from DuPont; those under the tradedesignation Profax® from Hercules;

those under the trade designation RTP 2800 Series Compounds from RTP Co.under the designators RTP 2801-40D, RTP 2802-40D, ESD A 2800 and ESD C2800; those under the trade designation Multi-Flex® from Multibase, Inc.under the designators Multi-Flex TPE® and Multi-Flex TPO; those underthe trade designation Dynaflex® and Versaflex™ from GLS Corporation.

Olefinic thermoplastic elastomers are described in U.S. Pat. Nos.5,856,399; 5,847,052; 5,786,403; 5,728,744; 5,702,827; 5,596,042;5,552,482; 5,449,711; 5,349,005; 5,191,005; 4,985,497; 4,933,389;4,908,412; 4,833,194; and 4,340,684; and these disclosures areincorporated herein for there descriptions of olefinic thermoplasticelastomers. Chlorinated olefinic thermoplastic elastomers are describedin U.S. Pat. Nos. 5,728,772; 5,717,028; 5,387,648; 5,314,941; 5,286,795;5,270,381; 5,237,010; 4,978,716; 4,978,703; 4,910,245; 4,739,012;4,728,692, 4,627,993; and 4,613,533; and these disclosures areincorporated herein for there descriptions of chlorinated olefinicthermoplastic elastomers.

A suitable amount of an adhesive is applied to at least one of thethermoplastic elastomer and the magnesium containing metal, then thethermoplastic elastomer is contacted with the magnesium containingmetal. The adhesive forms a strong bond between the thermoplasticelastomer and the magnesium containing metal, despite the environment.

Generally speaking the adhesive is applied to at least one of thethermoplastic elastomer and the magnesium containing metal by brushing,spraying, or dipping. Optionally, heat and/or pressure is applied tofacilitate formation of a strong bond between the thermoplasticelastomer and the magnesium containing metal.

The adhesive is preferably applied via a solvent of diluent wherein afilm is formed on at least one of the thermoplastic elastomer and themagnesium containing metal. In one embodiment, the adhesive filmthickness is from about 0.01 mils to about 20 mils. In anotherembodiment, the adhesive film thickness is from about 0.1 mils to about10 mils. In yet another embodiment, the adhesive film thickness is fromabout 0.5 mils to about 2 mils.

In one embodiment, the temperature at which the thermoplastic elastomerand the magnesium containing metal are bonded or brought together isfrom about 20° C. to about 300° C. In another embodiment, thetemperature at which the thermoplastic elastomer and the magnesiumcontaining metal are bonded is from about 50° C. to about 250° C. In yetanother embodiment, the temperature at which the thermoplastic elastomerand the magnesium containing metal are bonded is from about 100° C. toabout 200° C. In the specific embodiment where the thermoplasticelastomer is Alcryn®, the bonding temperature is from about 170° C. toabout 180° C.

In one embodiment, the pressure under which the thermoplastic elastomerand the magnesium containing metal are bonded is from about 500 psi toabout 6,000 psi. In another embodiment, the pressure under which thethermoplastic elastomer and the magnesium containing metal are bonded isfrom about 1,000 psi is to about 5,000 psi. In yet another embodiment,the pressure under which the thermoplastic elastomer and the magnesiumcontaining metal are bonded is from about 2,000 psi to about 4,500 psi.

In one embodiment, the time under which pressure is applied to thethermoplastic elastomer and the magnesium containing metal for bondingis from about 1 second to about 1 minute. In another embodiment, thetime under which pressure is applied to the thermoplastic elastomer andthe magnesium containing metal for bonding is from about 2 seconds toabout 30 seconds. In yet another embodiment, the time under whichpressure is applied to the thermoplastic elastomer and the magnesiumcontaining metal for bonding is from about 3 seconds to about 15seconds.

In one embodiment, the adhesive is preferably a heat-activated solventbased adhesive. An example of a commercially available adhesive inaccordance with the present invention include those under the tradedesignation Chemlok® from Lord Corp.; and specifically those under thedesignators Chemlok® 480 and Chemlok® Curative 44.

Suitable adhesives in accordance with the present invention includethose described in U.S. Pat. Nos. 5,268,404; 5,051,474; 5,019,608;4,857,131; and 4,119,587; and these disclosures are incorporated hereinfor there descriptions of adhesives.

The adhesive contains a polymeric material. The polymeric materialcontains at least one of a halogenated polymer, such as a halogencontaining polyolefin, a butadiene polymer latex, and a polyesterpolyurethane. In one embodiment, the adhesive contains from about 20% toabout 99% by weight of one or more polymeric materials. In anotherembodiment, the adhesive contains from about 30% to about 97% by weightof one or more polymeric materials. In another embodiment, the adhesivecontains from about 40% to about 95% by weight of one or more polymericmaterials.

The adhesive further contains at least one polymeric complimentarymaterials. Polymeric complimentary materials include at least one of anaromatic-nitroso compound, a lead acid or metal oxide, a maleimidecompound, a vulcanization agent, a phenolic epoxy resin, a phenolicresin, a crosslinking compound, a methylene donor compound, variousorganic solvents and/or diluents, and water. In one embodiment, theadhesive contains from about 1% to about 80% by weight of one or morepolymeric complimentary materials. In another embodiment, the adhesivecontains from about 3% to about 70% by weight of one or more polymericcomplimentary materials. In yet another embodiment, the adhesivecontains from about 5% to about 60% by weight of one or more polymericcomplimentary materials.

Next, four specific embodiments of the adhesive are described in detail.The first three embodiments are solvent based adhesives that may also beused as heat-activated solvent based adhesives. The fourth embodiment isan aqueous based adhesive. The solvent based adhesives are preferred.

In one embodiment, the adhesive is an organic solvent based adhesive andcontains at least one halogenated polymer, at least one aromatic nitrosocompound; at least one lead salt of certain organic and/or inorganicacids; and, optionally, at least one maleimide compound. In thisembodiment, the aromatic nitroso compound is pressman an amount in therange from about 1 to about 200, preferably from about 10 to about 100,parts by weight per 100 parts by weight of the halogen-containingpolyolefin. The amount of lead salt is normally in the range from about10 to about 150 parts, preferably from about 25 to about 100, and mostpreferably from about 35 to about 75, parts by weight per 100 parts byweight of the halogen-containing polyolefin. The herein-describedadhesive compositions can be compounded with an appropriate inertsolvent or diluent to provide an adhesive lacquer having a total solidscontent (TSC) in the range from about 5% to about 80%, preferably about15% to about 40%. Alternatively, the adhesive compositions can beprovided at 100% TSC in the form of an adhesive film or tape. Ifdesired, conventional additives such as are normally used in adhesivecompositions can be included with the amount of such additives beingwithin the ranges conventionally employed.

Optionally, there can be incorporated into the adhesives from about 0.5to about 25, preferably from about 2 to about 20, parts by weight, per100 parts by weight of the halogen-containing polymer, of at least onemaleimide compound. The use of such maleimide compounds in the adhesivescontributes to augment environmental resistance in particularlyaggressive or harsh environments.

The halogen-containing polymers are halogen-containing natural andsynthetic polyolefinic elastomers. The halogens employed in thehalogenated polyolefinic elastomers are usually chlorine or bromine,although fluorine can also be used. Mixed halogens can also be employedin which case the halogen-containing polyolefin has more than onehalogen substituted thereon. The amount of halogen is not critical andcan range from as low as about 3% by weight to more than about 70% byweight, depending on the nature of the base polymer.

Halogen-containing polyolefinic elastomers and their preparation areknown in the art. Representative halogen-containing polyolefinicelastomers include chlorinated natural rubber, chlorine- andbromine-containing synthetic rubbers including polychloroprene,chlorinated polychloroprene, chlorinated polybutadiene, chlorinatedbutadienestyrene copolymers, chlorinated ethylene-propylene copolymersand ethylene/propylene/non-cojugated diene terpolymers, chlorinatedpolyethylene, chlorosulfonated polyethylene, brominatedpoly(2,3-dichloro-1,3-butadiene), copolymers of alphachloroacrylonitrileand 2,3-dichloro-1,3-butadiene, chlorinated poly(vinyl chloride),halogenated copolymers of dissimilar α-olefins having from about 2 toabout 8 carbon atoms, and the like, including mixtures of suchhalogen-containing elastomers. Representative halogen-containingpolyolefinic elastomers further include halogenated vinyl halidepolymers-including halogenated homopolymers or copolymers of vinylhalide. These halogenated materials can be made by post-halogenating thevinyl-halide resin, preferably by post-chlorinating polyvinylchloride.Such materials are commercially available under the trade designationsGenchlor S and Genchlor T from Imperial Chemical Industries, Ltd.Generally speaking, any of the known halogen-containing derivatives ofnatural and synthetic elastomers can be employed in the adhesives,including mixtures of such elastomers. In a preferred embodiment,chlorosulfornated polyethylene elastomers alone or in combination withchlorinated natural rubber are employed as halogen-containingfilm-forming polymers.

The aromatic nitroso compounds are aromatic hydrocarbons, such asbenzenes, naphthalenes, anthracenes, biphenyls, and the like, containingat least about two nitroso groups attached directly to non-adjacent ringcarbon atoms. More particularly, such nitroso compounds are described aspoly-C-nitroso aromatic compounds having from 1 to about 3 aromaticnuclei, including fused aromatic nuclei, having from about 2 to about 6nitroso groups attached directly to non-adjacent nuclear carbon atoms.Preferred poly-C-nitroso materials are the di-nitroso aromaticcompounds, especially the dinitrosobenzenes and dinitrosonaphthalenes,such as the meta- or paradinitrosobenzenes and the meta- orparadinitrosonaphthalenes. The nuclear hydrogen atoms of the aromaticnucleus can be replaced by alkyl, alkoxy, cycloalkyl, aryl, aralkyl,alkaryl, arylamine, arylnitroso, amino, halogen, and the like groups.The presence of such substituents on the aromatic nucleus has littleeffect on the activity of the poly-C-nitroso compounds in the presentinvention. The substituents can be organic or inorganic in nature. Thus,where reference is made herein to poly-C-nitroso or di-C-nitroso“aromatic compound”, “benzenes”, or “naphthalenes”, it is understood toinclude both substituted and unsubstituted nitroso compounds, unlessotherwise specified.

In a preferred embodiment, poly-C-nitroso compounds are characterized bythe formula

(R^(o))_(m)—Ar—(NO)₂,

wherein Ar is selected from the group consisting of phenylene andnaphthalene: R⁰ is one or more monovalent organic radicals of alkyl,cycloalkyl, aryl, aralkyl, alkaryl, arylamine and alkoxy radicals havingfrom 1 to about 20 carbon atoms, amino, or halogen, and is preferably analkyl group having from 1 to about 8 carbon atoms; and m is zero, 1, 2,3 or 4 and preferably is zero.

A partial listing of suitable poly-C-nitroso compounds includem-dinitrosobenzene, p-dinitrosobenzene, m-dinitrosonaphthalene,p-dinitrosonaphthalene, 2,5-dinitroso-p-cymene,2-methyl-1,4-dinitrosobenzene, 2-methyl-5-chloro-1,4-dinitrosobenzene,2-fluoro-1,4-dinitrosobenzene, 2-methoxy-1-3-dinitroso- benzene,5-chloro-1,3-dinitrosobenzene, 2-benzyl-1,4-dinitrosobenzene, and2-cyclohexyl-1,4-dinitrosobenzene.

The lead salts are generally polybasic lead salts of phosphorous acidand saturated and unsaturated organic dicarboxylic acids and acidanhydrides. These lead salts are commercially available. Preferred leadsalts include dibasic lead phthalate, monohydrous tribasic lead maleate,tetrabasic lead fumarate, and dibasic lead phosphite, and mixtures oftwo or more thereof. Although not fully understood and not wishing to bebound by any theory, it is believed that the lead salts contribute toenvironmental resistance, possibly by acting as acid acceptors foracidic materials which may undesirably be present.

Maleimide compounds include all of the maleimide, bismaleimide andrelated compounds which are described in U.S. Pat. Nos. 2,444,536 and2,462,835, which disclosures are herein incorporated by reference inthis regard. Preferred maleimide compounds include the N,N′-linkedbis-maleimides which are either joined directly at the nitrogen atomswithout any intervening structure or in which the nitrogen atoms arejoined to and separated by an intervening divalent radical such asalkylene, cycloalkylene, oxydimethylene, phenylene (all 3 isomers),2,6-dimethylene-4-alkylphenol, or sulfonyl, m-phenylene-bis-maleimide. Apreferred compound is available under the trade designation “HVA-2” fromDu Pont.

Instead of a maleimide compound as described in the paragraph above, apolymaleimide compound may be used. The polymaleimide compound is analiphatic or aromatic polymaleimide and preferably contains at least twomaleimide groups. Aromatic polymaleimides having from about 1 to about100 aromatic nuclei wherein the maleimide groups are directly attachedto each adjacent aromatic ring are especially preferred. Particularlypreferred polymaleimide compounds have the formula:

wherein x is from about 1 to about 100. Such polymaleimides arecommercially 1 5 available from a number of sources including under thetrade designation BMI-M-20 polymaleimide from Mitsui Toatsu FineChemicals, Inc. The amount of polymaleimide compound used in theadhesive may be from about 5 to about 100 parts by weight per 100 partsof the halogen-containing polyolefin and preferably from about 10 toabout 60 parts.

The adhesives of this embodiment are prepared by conventional means. Forexample, the components can be mixed and dispersed in an inert liquidcarrier which, once the adhesive is applied to the thermoplasticelastomer or the magnesium containing metal, can be readily evaporated.Examples of suitable carriers are aromatic and halogenated aromatichydrocarbons such as benzene, ethyl benzene, toluene, xylene,chlorobenzene, dichlorobenzene, and the like; halogenated aliphatichydrocarbons such as trichloroethylene, perchloroethylene, propylenedichloride, and the like; ketones such as methyl ethyl ketone, methylisobutyl ketone, and the like; ethers, naphthas, etc., includingmixtures of two or more thereof. In a preferred embodiment, the carrieris at least one of xylene and methyl ethyl ketone. The amount of thecarrier is not critical, but ordinarily provides a total solids contentranging from about 5% to about 80%, preferably about 15% to about 40% byweight. Alternatively, the adhesives can be compounded as 100% TSCsystems which contain no solvent or diluent and provided in the form ofan adhesive tape or film.

The adhesives are applied to at least one of the surfaces of thethermoplastic elastomer and/or the magnesium containing metal in aconventional manner such as by dipping, spraying, brushing, and thelike. Preferably, the surfaces to which the adhesive is applied isallowed to dry after coating before being brought together for bonding.After the surfaces are pressed together with the adhesive layertherebetween, the assembly of the thermoplastic elastomer and themagnesium containing metal may be heated in accordance with conventionalpractices. The exact conditions selected depend upon the particularelastomer being bonded and whether or not it is cured. The conditionsare generally at a temperature from about 140° C. to about 200° C. for atime from about 5 minutes to about 60 minutes. Alternatively, thebonding temperature may range from about 90° C. to above about 180° C.for a time from about 15 minutes to about 120 minutes. Alternatively, insituations where applicable, the adhesives can be interspersed betweenthe surfaces to be joined as a solid film or tape (100% TSC adhesivesystem) with bonding being accomplished as before.

In a second embodiment, the adhesive is an organic solvent basedadhesive and contains a one-coat rubber-to-metal adhesive containing atleast one halogen-containing polyolefin; from about 1 to about 200 partsby weight, per 100 parts by weight of the halogen-containing polyolefin,of at least one aromatic nitroso compound; from about 10 to about 120parts by weight per 100 parts by weight of the halogen-containingpolyolefin of at least one metal oxide of zinc oxide and magnesiumoxide; from zero to about 25 parts by weight, per 100 parts by weight ofthe halogen-containing polyolefin, of at least one maleimide compound;from zero to about 40 parts by weight, per 100 parts by weight of thehalogen-containing polyolefin, of at least one vulcanizing agent ofsulfur and selenium; from zero to about 80 parts by weight, per 100parts by weight of the halogen-containing polyolefin of a phenolic epoxyresin; and an inert diluent, the diluent being present in an amount toprovide a lacquer type composition suitable for use as an adhesive, thelacquer having a total solids content in the range from about 5% toabout 80%.

Halogen-containing polyolefins, nitroso compounds, maleimide compounds,and diluents are the same as those described in the embodiment above,and thus they are not repeated here.

The metal oxides include one or more of zinc oxide and magnesium oxide.These metal oxides are commercially available. Although not fullyunderstood and not wishing to be bound by any theory, it is believedthat the metal oxides contribute to environmental resistance, possiblyby acting as an amphoteric material, reacting with acids to form salts,thereby acting as an acid scavenger.

Furthermore, such metal oxides are known curing activators in thevulcanization of rubber. When using such metal oxides, it is notgenerally necessary to employ lead containing compounds, thus thisembodiment provides a lead-free adhesive. The amount of metal oxide usedin the adhesive may be from about 10 to about 120 parts by weight per100 parts of polyolefin and preferably from about 12 to about 80 parts.

The vulcanizing agents include at least one of sulfur and selenium. Thevulcanizing agents are commercially available. The amount of vulcanizingagent used in the adhesive may be from 0 to about 40 parts by weight per100 parts of the halogen-containing polyolefin and preferably from about5 to about 30 parts.

The metal oxide component and the vulcanizing agent component of theadhesive composition are added in finely divided form or as a dispersionin a suitable liquid carrier.

Phenolic epoxy resins generally include the polyglycidyl polyethers ofpolyhydric phenols. These phenolic-epoxy resins are complex polymericreaction products of polyhydric phenols with polyfunctional holohydrinsand/or glycerol dichlorohydrin. The products thus obtained containterminal epoxy groups. A large number of epoxy resins of this type aredisclosed in U.S. Pat. Nos. 2,585,115 and 2,589,245, which are herebyincorporated by reference for there disclosure of phenolic-epoxy resins.Several of these resins are commercially available.

Typical polyhydric phenols useful in the preparation of the phenolicepoxy resins include resorcinal and novolac resins resulting fromcondensation of phenol with formaldehyde. The phenol/formaldehyde molarratio, coupled with the type of catalyst, determines whether theresulting polymer is phenol terminated or methylol terminated;phenol-terminated are referred to as novolacs. These are produced from areaction mixture having a formaldehyde/phenol molar ratio between about0.5 and about 0.8 in the presence of an acid catalyst. Resorcinal is avery reactive dihydric phenol with formaldehyde, allowing for thepreparation of resorcinal-formaldehyde novolacs.

A typical phenolic epoxy resin prepared from the novolac resins andepichlorohydrin has the following structural formula:

In which R is hydrogen or an alkyl group having from 1 to about 4 carbonatoms and n has a range from 1 to about 8.

Phenolic epoxy resins may be further characterized by reference of theirepoxy weight of pure epoxy resins being the mean molecular weight of theresin divided by the mean number of epoxy radicals per molecule or inany case the number of grams of epoxy resin equivalent to one mole ofthe epoxy group or one gram equivalent of epoxide. The phenolic epoxyresins that may be used in this embodiment have an epoxy equivalentweight from about 400 to about 1000. The amount of phenolic epoxy resinsused in the adhesive may be from 0 to about 80 parts by weight per 100parts by weight of the the halogen-containing polyolefin, and preferablyfrom about 2 to about 50 parts.

In a third embodiment, the adhesive contains two components and is anorganic solvent based adhesive. The first component of the adhesive inthis embodiment comprises a linear polyester polyurethane, a halogenatedpolyolefin and a phenolic resin. Halogen-containing polyolefins orhalogenated polyolefin and diluents are the same as those described inthe embodiments above, and thus they are not repeated here.

The linear polyester polyurethanes are typically prepared by reactingisocyanate-functional urethane polyester prepolymers with low molecularweight chain extending diols employing conventional techniques known inthe art. An extensive description of some of the useful techniques forpreparing polyester urethane prepolymers can be found in Saunders andFrisch: “Polyurethanes, Chemistry and Technology,” Part II,Interscience, (New York 1 964), especially at pages 8 to 49, and in thereferences cited therein. Other preparative techniques which are knownin the art can also be employed.

More specifically, the linear polyester polyurethanes which can beemployed in the adhesive of this embodiment typically are preparedby-reacting at least one linear polyester having two active hydrogenatoms with a diisocyanate in order to form an isocyanate-functionalurethane polyester prepolymer. The urethane polyester prepolymer is thenreacted with a low molecular weight chain extending diol in order toprepare the linear polyester polyurethane.

The hydrogen atom-containing linear polyesters used to produce thepolyurethanes are generally hydroxy-terminated polyesters having anaverage molecular weight in the range from about 500 to about 4000. Thelinear polyesters are typically formed from bifunctional monomers havingeither aliphatic or aromatic segments therein. For example, the linearpolyesters may be formed by reacting polyhydric alcohols withpolycarboxylic acids in hydroxyl:carboxyl ratios ranging from about 2:1to about 15:14. Exemplary linear polyesters useful for forming thepolyurethanes include condensation products of adipic acid orterephthalic acid with 1,4-butane diol or ethylene glycol.

Any diisocyanates having two reactive isocyanate groups can be reactedwith the linear polyester in order to create the isocyanate-functionalurethane polyester prepolymers. Such diisocyanates include diisocyanatessuch as 1,6-hexamethylene diisocyanate; 1,8-octomethylene diisocyanate;1,12-dodecamethylene diisocyanate; 2,2,4-trimethylhexamethylenediisocyanate and similar isocyanates; 3,3′diisocyanatodipropyl ether;3-isocyanatomethyl-3,5,5′-trimethylcyclohexyl isocyanate;cyclopentalene-1,3-diisocyanate; cyclohexylene-1,4-diisocyanate; methyl2,6-diisocyanatocaprolate; bis-(2-isocyanatoethyl)-fumarate;4-methyl-1,3-diisocyanatocyclohexane; trans-vinylene diisocyanate andsimilar unsaturated polyisocyanates;4,4′-methylene-bis-(cyclohexylisocyanate) and related polyisocyanates;methane diisocyanates; bis-(2-isocyanatoethyl) carbonate and similarcarbonate polyisocyanates; N,N′N-tris-(6-isocyanatohexamethylene) biuretand related polyisocyanates as well as other known polyisocyanatesderived from aliphatic polyamines; toluene diisocyanates;xylene-diisocyanates; dianisidine diisocyanate; 4,4′-diphenylmethanediisocyanate; 1-ethoxy-2,4-diisocyanatobenzene;1-chloro-2,4-diisocyanatobenzene; tris(4-isocyanatophenyl) methane;naphthalene diisocyanates; 4,4′-biphenyl diisocyanate; phenylenediisocyanates; 3,3′-dimethyl-4,4′-biphenyl diisocyanate;p-isocyanatobenzoyl isocyanate and tetrachloro-1,3-phenylenediisocyanate and mixtures thereof. Preferred diisocyanates includetoluene diisocyanate and diphenylmethane-4,4′-diisocyanate.

The urethane polyester prepolymer is reacted with low molecular weightchain extending diols as is known in the art to produce the final linearpolyester polyurethane. Typical chain extending diols include 1,4-butanediol and ethylene glycol.

Generally, the polyurethane employed has a molecular weight of at leastabout 50,000, but preferably has a molecular weight greater than about100,000. In a preferred embodiment, the linear polyester polyurethanesare prepared by reacting a linear polyester with toluene diisocyanateand chain extending the prepolymer thus formed with 1,4-butane diol. Theurethane preferably has a hydroxyl content of between about 0.08% andabout 0.12% and a solution viscosity (15% by weight in methyl ethylketone) of between about 400 and about 800 centiposes. The linearpolyester polyurethane is utilized in an amount from about 10% to about99%, preferably from about 60% to about 80% by weight of the firstcomponent.

The halogenated polyolefin is normally utilized in an amount from about0.2% to about 60% by weight, preferably from about 15% to about 30% byweight of the first component.

The phenolic resins generally include phenol-aldehyde condensates. Suchresins are prepared according to known methods by condensing phenoliccompounds and aldehydes, usually under acidic to neutral conditions.Also included within the purview of phenolic resins are the reactionproducts obtained by further condensing a formed resole resin withadditional phenolic compound. For more detailed information regardingphenolic resins, including methods of preparation, see Carswell“Phenoplasts,” Interscience Publishers, Inc., New York, N.Y., (1 947),which treatise is incorporated herein by reference. Suitable phenolicresins include resinous oils as well as pulverulent solids.

In forming the phenolic resins, there can be utilized a variety ofphenolic compounds, i.e., both monohydroxy and polyhydroxy phenols,including such compounds having at least one aromatic nucleus, andsubstituted derivatives thereof, and including mixtures of two or moreof such phenolic compounds. Among the substituent groups which can beattached to the nucleus of the phenolic compound are alkyl, alkoxy,amino, halogen and the like. Representative phenolic compounds includephenol, p-t-butylphenol, p-phenylphenol, p-chlorophenol, p-alkoxyphenol,o-cresol, m-cresol, o-chlorophenol, m-bromophenol, 2-ethylphenol, amylphenol, nonyl phenol, cashew nut shell liquid, resorcinol, orcinol,pyrocatechol, pyrogallol, salicylic acid, bis-phenol A, bis-phenol S,and the like. Preferred phenolic resins are obtained when the phenolicprecursors comprise: about 100 mole percent of at least one polyhydroxyphenol such as resorcinol, pyrogallol, catechol and the like; from about50 to about 98, preferably about 60 to about 98, mole percent of atleast one polyhydroxy phenol and from about 50 to about 2, preferablyabout 40 to about 2, mole percent of at least one monohydric phenol, thenucleus of which is not substituted with a hydrocarbon radical, i.e. aradical containing only carbon and hydrogen atoms, although the nucleuscan be substituted with groups such as alkoxy, amino, halogen, and thelike; and from about 10 to about 98, preferably about 50 to about 98mole percent of at least one polyhydroxy phenol and from about 90 toabout 2, preferably about 50 to about 2, mole percent of at least onemonohydric phenol, the-nucleus of which is substituted 100 with at leastone alkyl group having from 1 to about 22 carbon atoms; or about 100mole percent of at least one monohydric phenol, the nucleus of which issubstituted with at least one alkyl group having from 1 to about 22carbon atoms; said mole percent being based on total moles of phenoliccompound.

Particularly preferred phenolic resins are obtained by utilizing amixture of pyrogallol and resorcinol as the phenolic precursors.Specifically, a phenolic resin prepared from a mixture containing fromabout 1 to about 99, preferably about 20 to about 80 mole percent ofpyrogallol and from about 99 to about 1, preferably about 80 to about 20mole percent of resorcinol provides excellent adhesion.

Representative aldehydes which can be condensed with phenolic compoundsto form phenolic resins include formaldehyde, acetaldehyde,propionaldehyde, isobutyraldehyde, 2-ethylbutyraldehyde, glyceraldehyde,2-methylpentaldehyde, 2-ethylhexaldehyde, as well as compounds whichdecompose to formaldehyde, such as paraformaldehyde, trioxane, furfural,hexamethylenetetramine, acetals which liberate formaldehyde on heatingbenzaldehyde, and the like. The preferred aldehyde is formaldehyde. Thealdehyde is typically utilized in an amount ranging from about 20 toabout 90, preferably from about 40 to about 80 mole percent per 100 molepercent of the total phenolic precursor or precursor mixture to producethe phenolic resin.

The phenolic resin is typically utilized in an amount from about 0.5% toabout 20%, preferably from about 2% to about 13% by weight of the firstcomponent.

The second component of this embodiment is a cross-linking compoundwhich cross-links or cures the first component. The cross-linkingcompound can essentially be any material which will effectively cure orcross-link the first component. The cross-linking compound is preferablya diisocyanate compound such as 2,4-toluene diisocyanate,diphenylmethane-4,4′-diisocyanate, p-phenylene diisocyanate, m-phenylenediisocyanate, 1,4-cyclohexyl diisocyanate, tetramethylxylyl diisocyanateand dimethylbiphenyl diisocyanate, withdiphenylmethane-4,4′-diisocyanate being the preferred diisocyanatecompound. The cross-linker is typically utilized in an amount from about4 to about 32, preferably from about 8 to about 20 parts by weight per100 parts by weight of the first component.

A solvent is required to dissolve the respective components. Solventsused for dissolving the first component include polar or aromaticsolvents such as methyl ethyl ketone, methyl isobutyl ketone, xylene andtoluene, with methyl ethyl ketone and xylene being preferred. Thesolvent for the first component is utilized in an amount sufficient toprovide a component having a total solids content (TSC) of from about 10to about 50, preferably from about 15 to about 30. A solvent, althoughnot necessary, may be utilized to dissolve the second component. Typicalsolvents useful for dissolving the second component include halogenatedsolvents such as 1,1,1-trichloroethane and perchloroethylene with1,1,1-trichloroethane being preferred. The solvent for the secondcomponent is utilized in an amount sufficient to provide a componenthaving a total solids content of from about 1 to about 100, preferablyfrom about 30 to about 60.

The adhesive of this third embodiment can optionally contain otherwell-known additives. The two components of this embodiment must bestored separately in order to avoid any premature cross-linking orcuring of the adhesive. The adhesive is typically applied to at leastone of the thermoplastic elastomer and the magnesium containing metal byfirst mixing the first component and the second component together inthe amounts described previously. After the initial mixing, theresulting formulation must be applied within at least about 30 days butpreferably within about 2 days in order to avoid a premature increase inviscosity. Most preferably, the formulation is applied immediately aftermixing the two components in order to avoid any increase in viscositywhich might create problems associated with the correspondingapplication technique. The formulation may be applied to a desiredsubstrate by techniques known in the art such as by brushing, spraying,or dipping. Preferably, the formulation is applied by dipping orbrushing.

In general, after applying the adhesive and allowing it to dry for aperiod of between about 12 and about 24 hours, the surfaces of thethermoplastic elastomer and the magnesium containing metal to be bondedare brought together under at least about 1 psi/sq. in. of pressure inorder to create a permanent bond. Additional heating may be employed butis not required to effect the bonding.

The magnesium containing metal and the thermoplastic elastomer aretypically brought together under a pressure from about 500 psi to about5,000 psi, preferably from about 2,000 psi to about 4,500 psi.Additional heating may be provided but is not required for the adhesiveof the invention to sufficiently bond the thermoplastic elastomer to themagnesium containing metal. After the thermoplastic elastomer andmagnesium containing metal are brought together, the elastomer-magnesiumcontaining metal assembly is preferably allowed to cool for a period offrom about 12 hours to about 24 hours in order to ensure sufficientcross-linking of the adhesive.

In a fourth embodiment, the adhesive is an aqueous based adhesive andcontains a polyvinyl alcohol stabilized butadiene polymer latex incombination with a methylene donor compound. The butadiene latices canbe prepared by polymerizing appropriate monomers in an aqueous solutionof polyvinyl alcohol. The butadiene polymer of this embodiment can beprepared from butadiene monomers alone or from a combination ofbutadiene monomers and other copolymerizable monomers described in moredetail below. Butadiene polymer as used herein refers to butadienehomopolymers, butadiene copolymers, butadiene terpolymers and higherpolymers.

The butadiene monomers useful for preparing the butadiene polymer of thelatex can essentially be any monomer containing conjugated unsaturation.Typical monomers include 2,3-dichloro- 1,3-butadiene; 1,3-butadiene;2,3-dibromo- 1,3-butadiene; isoprene; 2,3-dimethylbutadiene;chloroprene; bromoprene; 2,3-dibromo-1,3-butadiene;1,1,2-trichlorobutadiene; cyanoprene; hexachlorobutadiene andcombinations of two or more thereof. It is particularly preferred to use2,3-dichloro-1,3-butadiene as the butadiene monomer since butadienehomopolymers derived from 2,3-dichloro-1,3-butadiene or butadienecopolymers wherein a major portion of the polymer contains2,3-dichloro-1,3-butadiene monomer units are particularly useful inadhesive applications.

Copolymerizable monomers herein refers to monomers which are capable ofundergoing copolymerization with the butadiene monomers described above.Typical copolymerizable monomers include a-haloacrylonitriles such asα-bromoacrylonitrile and α-chloroacrylonitrile; α,β-unsaturatedcarboxylic acids such as acrylic, methacrylic, 2-ethylacrylic,2-propylacrylic, 2-butylacrylic and itaconic acids;alkyl-2-haloacrylates such as ethyl-2-chloroacrylate andethyl-2-bromoacrylate; styrene; styrene sulfonic acid; α-halostyrenes;chlorostyrene; α methylstyrene; α-bromovinylketone; vinylidene chloride;vinyl toluenes; vinylnaphthalenes; vinyl ethers, esters, and ketonessuch as methyl vinyl ether, vinyl acetate, and methyl vinyl ketone;esters, amides, and nitriles of acrylic and methacrylic acids such asethyl acrylate, methyl methacrylate, glycidyl acrylate, methacrylamide,and acrylonitrile; and combinations of two or more such monomers.

The copolymerizable monomers, if utilized, are preferablyα-halo-acrylonitrile and/or α,β-unsaturated carboxylic acid monomers.The copolymerizable monomers are utilized in an amount ranging fromabout 0.1% to about 30% by weight of the total monomers utilized to formthe butadiene polymer.

Two butadiene polymers which are particularly useful in adhesiveapplications include a butadiene copolymer prepared from butadienemonomers and α-halo-acrylonitrile monomers wherein theα-haloacrylonitrile monomers comprise from about 1% to about 29%,preferably about 5% to about 20% by weight of the total monomers, and abutadiene terpolymer prepared from butadiene monomers,α-haloacrylonitrile monomers, and α,β-unsaturated carboxylic acidmonomers, wherein the α-haloacrylo-nitrile monomers comprise from about1% to about 29%, preferably about 5% to about 20% by weight and theα,β-unsaturated carboxylic acid monomers comprise from about 0.1% toabout 10%, preferably about 0.1% to about 1% by weight of the totalmonomers utilized.

The polyvinyl alcohol (PVA) of this embodiment can be any PVA,commercially or otherwise available, which dissolves in the presentaqueous polymerization system at the temperature of the polymerization.Such PVA is usually the product of hydrolysis of polyvinyl acetate,wherein the degree of hydrolysis is preferably about 80% to about 99%.The average degree of polymerization of the PVA is about 350-2,500. Fora general discussion of various PVAs, see The Encyclopedia of PolymerScience and Technology, Interscience Publishers, Vol. 14, pp. 149ff,(1971). The preferred proportion of PVA is about 3 to about 12,preferably about 6 to about 8, parts per 100 parts by weight of totalmonomers. The PVA acts as an emulsion stabilizer during thepolymerization.

It is presently preferred to utilize a stabilizing solvent incombination with the polyvinyl alcohol when preparing the latices. Thestabilizing solvent useful for preparing the improved latices canessentially be any organic solvent capable of exhibiting miscibilitywith water. The solvent is preferably an organic alcohol such asmethanol; ethanol; isopropanol; butanol; 2-(2-ethoxy ethoxy)ethanol;2-(2-butoxy ethoxy)ethanol; 2-(2-methoxy ethoxy)-ethanol; 2-methoxyethanol; 2-butoxy ethanol; 2-ethoxy ethanol; 2-butoxy propanol; 2-butoxyethoxy propanol and the propoxy propanols; also useful are known glycolsincluding ethylene and propylene glycols, and glycol derivatives such asethylene glycol mono-methyl ether and propylene glycol monomethyl ether.Various combinations of two or more the foregoing solvents may also beutilized. Preferred stabilizing solvents include methanol, ethanol,isopropanol, butanol, ethylene glycol monomethyl ether, and propyleneglycol monomethyl ether. The stabilizing solvent is typically utilizedin an amount ranging from about 10 to about 100, preferably from about30 to about 50, parts by weight per 100 parts by weight of totalmonomers. The stabilizing solvent is typically vacuum-stripped from thelatex after the emulsion polymerization so as to avoid the presence ofany volatile material in the final latex. In the case of higher boilingsolvents, the solvent may remain in the latex so as to yield a latexwhich does not require post polymerization stripping.

In carrying out the emulsion polymerization with the preferredstabilizing solvent to produce the latex, other optional ingredients maybe employed during the polymerization process. For example, conventionalanionic and/or nonionic surfactants may optionally be utilized in orderto aid in the formation of the latex. Typical anionic surfactantsinclude carboxylates, such as fatty acid soaps from lauric, stearic, andoleic acid; acyl derivatives of sarcosine, such as methyl glycine;sulfates, such as sodium laurel sulfate; sulfated natural oils andesters, such as Turkey Red Oil; alkyl aryl polyether sulfates; alkalialkyl sulfates; ethoxylated aryl sulfonic acid salts; alkyl arylpolyether sulfonates; isopropyl naphthalene sulfonates; sulfosuccinates;phosphate esters, such as short chain fatty alcohol partial esters ofcomplex phosphates; and orthophosphate esters of polyethoxylated fattyalcohols. Typical nonionic surfactants include ethoxylated (ethyleneoxide) derivatives, such as ethoxylated alkyl aryl derivatives; mono-and polyhydric alcohols; ethylene oxide/propylene oxide blockcopolymers; esters, such as glyceryl monostearate; products of thedehydration-of sorbitol, such as sorbitan monostearate and polyethyleneoxide sorbitan monolaurate; amines; lauric acid; and isopropenyl halide.A conventional surfactant, if utilized, is employed in an amount rangingfrom about 0.01 to about 15, preferably from about 0.1 to about 5 partsby weight per 100 parts by weight of total monomer.

Chain transfer agents may also be employed with the stabilizing solventduring the preferred emulsion polymerization of the adhesive in order tocontrol the molecular weight of the butadiene polymers and to modify thephysical properties of the resultant polymers as is known in the art.Any of the conventional organic sulfur-containing chain transfer agentsmay be utilized such as alkyl mercaptans, dialkyl xanthogen disulfidesand sodium thioglycolate. Typical alkyl mercaptans include dodecylmercaptan, octyl mercaptan, tert-dodecyl mercaptan, tridecyl mercaptan,and mixtures of mercaptans derived from coconut oil (often called laurylmercaptan), with dodecyl mercaptan being preferred.

The dialkyl xanthogen disulfides can be represented by the structure

wherein R¹ and R² independently are alkyl radicals having from 1 toabout 8 carbon atoms. Examples of suitable alkyl radicals are methyl,ethyl, propyl, isopropyl, and the various isomeric butyl, amyl, hexyl,heptyl and octyl radicals. Preferred dialkyl xanthogen disulfides arethose in which each alkyl radical has from 1 to about 4 carbon atoms,especially diisopropyl xanthogen disulfide.

A chain transfer agent, if utilized, is typically employed in an amountranging from about 0.1 to about 2, preferably from about 0.2 to about 1,parts by weight per 100 parts by weight of total monomer.

As stated above, the formation of the stable latices is preferablycarried out by emulsion polymerizing the appropriate monomers in thepresence of the polyvinyl alcohol and the stabilizing solvent.Specifically, an aqueous emulsification mixture of water, the polyvinylalcohol and the stabilizing solvent, is formed to which is added theappropriate monomers. The emulsification mixture typically contains fromabout 40% to about 80%, preferably about 50% to about 70% by weight ofwater.

The preferred emulsion polymerization with the stabilizing solvent istypically triggered by a free radical initiator. Typical free radicalinitiators include conventional redox systems, peroxide systems, azoderivatives, and hydroperoxide systems. The use of a redox system ispresently preferred for use include ammonium persulfate/sodiummetabisulfite, ferric sulfate/ascorbic acid/hydroperoxide andtributylborane/hydroperoxide. In a preferred embodiment, the redoxsystem utilizes (NH₄)₂S₂O₈ (ammonium persulfate) and Na₂S₂O₅ (sodiummetabisulfite). When utilizing this particular redox system, the Na₂S₂O₅is utilized to prepare the emulsification mixture. The (NH₄)₂S₂O₈ isthen added to the emulsification mixture along with the appropriatemonomers to initiate polymerization. Both the Na₂S₂O₅ and the (NH₄)₂S₂O₈are utilized in an amount ranging from about 0.1 to about 3, preferablyabout 0.2 to about 1, parts by weight per 100 parts by weight of totalmonomer.

The preferred emulsion polymerization with the stabilizing solvent istypically carried out at a temperature in the range from about 30° C. toabout 90° C., preferably about 40° C. to about 60° C. Monomer conversiontypically ranges from about 70% to 100%, preferably from about 80% toabout 100%.

The polyvinyl alcohol-stabilized butadiene latices typically have asolids content of between about 30% and about 70%, more typicallybetween about 40% and about 60%; a viscosity of between about 50 andabout 10,000 centipoise, preferably between about 100 and about 1,000centipoise; and a particle size between about 100 and about 300nanometers. The butadiene polymer of the latex typically has a molecularweight of between about 3,000 and about 300,000, preferably betweenabout 35,000 and about 100,000 Mn.

The polyvinyl alcohol-stabilized butadiene latices may also be preparedaccording to methods such as those disclosed in U.S. Pat. Nos. 3,920,600and 4,128,514, and in British Patent No. 1,469,993, which are herebyincorporated by reference in this regard.

The polyvinyl alcohol-stabilized butadiene polymer latex is typicallyutilized in the adhesive in this embodiment in an amount ranging fromabout 50% to about 99%, preferably from about 80% to about 97% by weightof the essential components of this embodiment. Essential components ofthis embodiment herein refers to the polyvinyl alcohol-stabilizedbutadiene polymer latex and the methylene donor compound describedhereinafter.

The methylene donor compound can essentially be any compound which iscompatible with the other ingredients of the adhesive and which iscapable of forming a methylene bridge or linkage between the freehydroxyl groups of the polyvinyl alcohol-stabilized butadiene latex atelevated temperatures. Typical elevated temperatures at which themethylene donor compound is capable of forming methylene bridges are inthe range from about 1 20° C. to about 1 95° C. Examples of methylenedonor compounds include hexamethylene tetramine, paraformaldehyde,s-trioxane, anhydro-formaldehydeaniline, ethylene diamine formaldehyde,methylol derivatives of urea and formaldehyde, acetaldehyde, furfural,methylol phenolic compounds, and the like.

The methylene donor compounds are preferably high molecular weightaldehyde homopolymers or copolymers. Typical high molecular weightaldehyde homopolymers and copolymers include acetal homopolymers; acetalcopolymers; gamma-polyoxy-methylene ethers having the characteristicstructure:

R³O—(CH₂O)_(n)—R⁴; and

polyoxymethylene glycols having the characteristic structure:

HO—(R⁵O)_(x)—(CH₂O)_(n)—(R⁶O)_(x)—H;

wherein R³ and R⁴ can be the same or different and each is an alkylgroup having from 1 to about 8, preferably 1 to about 4, carbon atoms;R⁵ and R⁶ can be the same or different and each is an alkylene grouphaving from about 2 to about 12, preferably from about 2 to about 8,carbon atoms; n is greater than about 100, and is preferably in therange from about 200 to about 2000; and x is in the range from 0 toabout 8, preferably 1 to about 4, with at least one x being equal to atleast 1. The high molecular weight aldehyde homopolymers and copolymersare further characterized by a melting point of at least about 75° C.,i.e., they are substantially inert with respect to the polyvinylalcohol-stabilized latex until heat activated; and by beingsubstantially completely insoluble in water at a temperature below themelting point. The acetal homopolymers and acetal copolymers arecommercially available. The polyoxymethylene materials are known and canbe readily synthesized by the reaction of monoalcohols having from 1 toabout 8 carbon atoms or dihydroxy glycols and ether glycols withpolyoxymethylene glycols in the presence of an acidic catalyst. Arepresentative method of preparing the polyoxymethylene materials isalso described in U.S. Pat. No. 2,512,950, which is incorporated hereinby reference. Gamma-polyoxymethylene ethers are the preferred methylenedonor compounds and a particularly preferred methylene donor compound is2-polyoxymethylene dimethyl ether.

The methylene donor compounds are typically utilized in an amountranging from about 1% to about 50%, preferably from about 3% to about20% by weight of the essentials components of the adhesive of thisembodiment.

The adhesive compositions of this embodiment may utilize one or morevarious optional ingredients selected from the group consisting of asupplemental polymeric film-forming component such as a halogenatedpolyolefin, a nitroso compound crosslinker, a maleimide compoundcrosslinker, a vulcanizing agent, an acid-scavenging compound and otheradditives, all of which are described in more detail above in connectionwith the other embodiments and thus are not repeated.

Optionally, additives conventionally employed with adhesivecompositions, such as fillers, dyes, pigments, extenders, dispersingagents, auxiliary film forming materials, and the like, can beincorporated into the adhesives of this invention for bonding athermoplastic elastomer with a magnesium containing metal.

The adhesives used in accordance with the present invention arecharacterized by excellent primary adhesion, environmental resistance,excellent shelf-life stability, resistance to sweep, pre-bakeresistance, good layover characteristics, and are effective over a broadspectrum of bonding temperatures, e.g., from about 25° C. to over about300° C.

The following examples illustrate the process of the present invention.Unless otherwise indicated in the following examples and elsewhere inthe written description and claims, all parts and percentages are byweight, all temperatures are in degrees Centigrade, and pressure is ator near atmospheric pressure.

EXAMPLE 1

An assembly of Multi-Flex® TPO, available from Multibase Inc., and amagnesium containing metal containing about 90% magnesium, about 10% andless than 1% of manganese. An adhesive containing about 92% by weightChemlok® 480 and about 8% Chemlok® Curative 44, both available from LordCorp., is mixed and applied to the cleaned surface of the magnesiumcontaining metal. The coated metal is optionally heated and then placedin an injection molding device. Hot Multi-Flex® TPO, between 150° C. and200° C. is injected into the mold. Molding is conducted under about2,800 psi for 10 seconds.

EXAMPLE 2

An assembly of Alcryn®, available from DuPont/Advanced Polymer Alloys,and a magnesium containing metal containing about 90% magnesium, about9% aluminum, about 0.7% zinc and about 0.3% manganese. An adhesivecontaining about 92% by weight Chemlok® 480 and about 8% Chemlok®Curative 44, both available from Lord Corp., is mixed and applied to thecleaned surface of the magnesium containing metal. The coated metal isoptionally heated and then placed in an injection molding device. HotAlcryn®, of about 175° C. is injected into the mold. Molding isconducted under about 4,000 psi for 6 seconds.

EXAMPLE 3

An assembly of Alcryn®, available from DuPont/Advanced Polymer Alloys,and a magnesium containing metal containing about 93% magnesium, about3% rare earth metals, about 3% zinc and about 1% zirconium. Themagnesium containing metal is dipped in a chromate bath containing about3 g/l of sodium dichromate. An adhesive containing about 92% by weightChemlok® 480 and about 8% Chemlok® Curative 44, both available from LordCorp., is mixed and applied to the chromate treated surface of themagnesium containing metal. The coated metal is optionally heated andthen placed in an injection molding device. Hot Alcryn®, of about 175°C. is injected into the mold. Molding is conducted under about 3,000 psifor 7 seconds.

The present invention also relates to products containing theaforementioned magnesium containing metal bonded to a thermoplasticelastomer with the adhesive. Such products include hand tools, datarecorders and other products, especially products used in harshenvironments, such as a manufacturing environment. In this connection, adata recorder made of a magnesium based metal and rubber may be made ofthe magnesium containing metal, thermoplastic elastomer and adhesiveaccording to the present invention.

While the foregoing Examples have been provided to aid the skilledartisan in more completely understanding the subject invention, they arenot intended to in any way limit the scope of the invention. The fullbreadth of the invention will be apparent to the skilled artisan uponreading the specification, and includes the use of any and all knownequivalent processes and materials.

What is claimed is:
 1. A method of making a bonded assembly comprising:applying an adhesive to at least a portion of a magnesium containingmetal to provide an adhesive coated metal, the adhesive comprising fromabout 20% to about 99% by weight of a polymeric material and themagnesium containing metal comprising at least about 25% by weightmagnesium, contacting the adhesive coated metal with a thermoplasticelastomer under a pressure from about 500 psi to about 6,000 psi for asufficient period of time to bond the thermoplastic elastomer to theadhesive coated metal.
 2. The method according to claim 1, wherein theadhesive coated metal is contacted with the thermoplastic elastomer at atemperature from about 50° C. to about 250° C.
 3. The method accordingto claim 1, wherein the period of time is from about 1 second to 1minute.
 4. The method according to claim 1, wherein the adhesive coatedmetal has an adhesive coating having a thickness from about 0.01 mils toabout 20 mils.
 5. The method according to claim 1, wherein the pressureis from about 1,000 psi to about 5,000 psi.
 6. The method according toclaim 1, wherein the period of time is from about 2 seconds to about 30seconds.
 7. The method according to claim 1, wherein the thermoplasticelastomer comprises an olefinic thermoplastic elastomer.
 8. The methodaccording to claim 1, wherein the thermoplastic elastomer comprises achlorinated olefinic thermoplastic elastomer.
 9. The method according toclaim 1, wherein the adhesive comprises from about 20% to about 99% byweight of at least one polymeric material and from about 1% to about 80%by weight of at least one polymeric complimentary material.
 10. A methodof making a bonded assembly comprising: applying an adhesive to at leasta portion of a magnesium containing metal to provide an adhesive coatedmetal, the adhesive comprising from about 20% to about 99% by weight ofa polymeric material and the magnesium containing metal comprising atleast about 25% by weight magnesium, contacting the adhesive coatedmetal with a chlorinated olefinic thermoplastic elastomer undersufficient pressure for a sufficient period of time to bond thethermoplastic elastomer to the adhesive coated metal.
 11. The methodaccording to claim 10, wherein the pressure is from about 500 psi toabout 6,000 psi.
 12. The method according to claim 10, wherein theadhesive coated metal is contacted with the thermoplastic elastomer at atemperature from about 20° C. to about 300° C.
 13. The method accordingto claim 10, wherein the period of time is from about 1 second to 1minute.
 14. A method of making a bonded assembly comprising: applying anadhesive to at least a portion of a chlorinated olefinic thermoplasticelastomer to provide an adhesive coated thermoplastic elastomer, theadhesive comprising from about 20% to about 99% by weight of a polymericmaterial and, contacting the adhesive coated thermoplastic elastomerwith a magnesium containing metal under sufficient pressure for asufficient period of time to bond the adhesive coated thermoplasticelastomer to the magnesium containing metal, the magnesium containingmetal comprising at least about 25% by weight magnesium.
 15. The methodaccording to claim 14, wherein the pressure is from about 500 psi toabout 6,000 psi.
 16. The method according to claim 14, wherein theadhesive coated thermoplastic elastomer is contacted with the magnesiumcontaining metal at a temperature from about 20° C. to about 300° C. 17.The method according to claim 14, wherein the period of time is fromabout 1 second to 1 minute.
 18. A method of making a bonded assemblycomprising: applying an adhesive to at least a portion of a magnesiumcontaining metal to provide; an adhesive coated metal, the adhesivecomprising from about 20% to about 99% by weight of a polymeric materialand the magnesium containing metal comprising at least about 25% byweight magnesium, contacting the adhesive coated metal with athermoplastic elastomer under sufficient pressure for a period of timefrom about 1 second to about 1 minute to bond the thermoplasticelastomer to the adhesive coated metal.
 19. The method according toclaim 18, wherein the thermoplastic elastomer comprises a chlorinatedolefinic thermoplastic elastomer.
 20. The method according to claim 18,wherein the polymeric material comprises at least one of a halogenatedpolymer, a butadiene polymer latex, and a polyester polyurethane.